Governance updates / MN sync

- Correct some reference links
 - Add MN sync info to guide
 - Update dseg, mnget, ssc, and govsync messages to include more detail

_includes/devdoc/guide_p2p_network.md

@@ -589,6 +589,40 @@ Earlier versions of Bitcoin Core allowed developers and trusted community member
 {% endautocrossref %}
 
 
+### Masternode Sync
+
+{% include helpers/subhead-links.md %}
+
+{% autocrossref %}
+
+Dash Core performs masternode synchronization as required, but it can be started
+manually by issuing the `mnsync reset` RPC command.
+
+*Masternode Sync Data Flow*
+
+| **Syncing Node Message** | **Direction**  | **Masternode Response**   | **Description** |
+| **1. Sporks** |   |  |  |
+| `getsporks` message                            | → |                           | Syncing node requests sporks
+|                                                | ← | `spork` message(s)        |
+| **2. Masternode List** |   |  | Sync Masternode list from other connected clients |
+| `dseg` message                                 | → |                           | Syncing node requests masternode list
+|                                                | ← | `ssc` message | Number of entries in masternode list (MASTERNODE_SYNC_LIST)<br><br>Only sent if requesting entire list
+|                                                | ← | `inv` message(s) (mnb)         | MSG_MASTERNODE_ANNOUNCE
+|                                                | ← | `inv` message(s) (mnp)         | MSG_MASTERNODE_PING
+| `getdata` message(s) (mnb) | → |                           | (Optional)
+| `getdata` message(s) (mnp)     | → |                           | (Optional)
+|                                                | ← | `mnb` message(s)          | (If requested) Masternode announce message
+|                                                | ← | `mnp` message(s)          | (If requested) Masternode ping message
+| **3. Masternode payments** |   |  | Ask node for all payment votes it has (new nodes will only return votes for future payments) |
+| `mnget` message                                | → |                           | Syncing node requests masternode payment sync
+|                                                | ← | `ssc` message | Number of entries in masternode payment list
+|                                                | ← | `inv` message(s) (mnw)         | MSG_MASTERNODE_PAYMENT_VOTE
+| `getdata` message(s) (mnw) | → |                           | (Optional)
+|                                                | ← | `mnw` message(s)          | (If requested) Masternode payment vote message
+| **4. Governance** |   |  | See [Governance sync](#governance) |
+
+{% endautocrossref %}
+
 
 ### Governance
 

_includes/devdoc/ref_p2p_networking.md

@@ -1855,8 +1855,9 @@ entry. To request the list of all masternodes, use an empty txIn (TXID of all
 zeros and an index of 0xFFFFFFFF).  To request information about a specific
 masternode, use the unspent output associated with that masternode.
 
-The response to a `dseg` message is an `mnb` message and an `mnp` message from
-the masternode(s) requested.
+The response to a `dseg` message is an `mnb` message inventory and an
+`mnp` message inventory for each requested masternode. Masternodes ignore this
+request if they are not fully synced.
 
 | Bytes | Name | Data type | Required | Description |
 | ---------- | ----------- | --------- | -------- | -------- |
@@ -1997,11 +1998,18 @@ Masternode Ping Message
 
 {% autocrossref %}
 
-The `mnget` message requests masternode payment sync.
+The `mnget` message requests masternode payment sync. The response to an
+`mnget` message is an `mnb` message inventory and an `mnp` message inventory for
+each requested masternode. Masternodes ignore this request if they are not fully synced.
 
 | Bytes | Name | Data type | Required | Description |
 | ---------- | ----------- | --------- | -------- | -------- |
-| 4 | nMnCount | int | Required |
+| 4 | nMnCount | int | Required | Number of masternode payment votes to request
+
+{% highlight text %}
+Note: Dash Core limits how frequently a masternode payment sync can be
+requested. Frequent requests will result in the node being banned.
+{% endhighlight %}
 
 The following annotated hexdump shows a `mnget` message. (The
 message header has been omitted.)
@@ -2156,7 +2164,10 @@ dd6cc6c11211793b239c2e311f1496e2
 
 {% autocrossref %}
 
-The `ssc` message is used to track the sync status of masternode objects.
+The `ssc` message is used to track the sync status of masternode objects. This
+message is sent in response to sync requests for masternode payments
+(`mnw` message), masternode list (`mnget` message),
+governance objects (`govsync` message), and governance object votes (`govsync` message).
 
 | Bytes | Name | Data type | Required | Description |
 | ---------- | ----------- | --------- | -------- | -------- |
@@ -2371,6 +2382,19 @@ dc45e9c09ee0427223e332b52e8d709e
 The `govsync` message is used to request syncing of governance objects
 (`govobj` message and `govobjvote` message) with peers.
 
+This message responds in two ways depending on the request:
+
+1. When a masternode receives a `govsync` message with a hash of all zeros, it
+responds with a `govobj` inventory message (MSG_GOVERNANCE_OBJECT - 0x17) for
+all valid governance objects. Governance object votes are excluded in this type
+of response.
+
+2. When a masternode receives a `govsync` message with a specific hash, it
+responds with both a `govobj` inventory message (MSG_GOVERNANCE_OBJECT - 0x17)
+and a `govobjvote` inventory message (MSG_GOVERNANCE_OBJECT_VOTE - 0x18) for
+the single goverance object requested.
+
+
 | Bytes | Name | Data type | Required | Description |
 | ---------- | ----------- | --------- | -------- | -------- |
 | 32 | nHash | uint256 | Required |

_includes/references.md

@@ -242,8 +242,8 @@ http://opensource.org/licenses/MIT.
 [getheaders message]: /en/developer-reference#getheaders "A P2P protocol message used to request a range of block headers"
 [getsporks message]: /en/developer-reference#getsporks "A P2P network message used to request the status of sporks"
 [govobj message]: /en/developer-reference#govobj "A P2P network message used to send governance objects"
-[govobjvote message]: /en/developer-reference#govobj "A P2P network message used to send governance object votes"
-[govsync message]: /en/developer-reference#govobj "A P2P network message used to synchronize governance objects"
+[govobjvote message]: /en/developer-reference#govobjvote "A P2P network message used to send governance object votes"
+[govsync message]: /en/developer-reference#govsync "A P2P network message used to synchronize governance objects"
 [headers message]: /en/developer-reference#headers "A P2P protocol message containing one or more block headers"
 [inv message]: /en/developer-reference#inv "A P2P protocol message used to send inventories of transactions and blocks known to the transmitting peer"
 [ix message]: /en/developer-reference#ix "A P2P protocol message which sends a single serialized transaction via InstantSend"